Filter holder, filter element and filter arrangement

ABSTRACT

A filter holder for a filter element that has an oval-shaped cross section, with a receiving section receiving the filter element, a fluid inlet and a fluid outlet. The fluid inlet is arranged such that an inflow direction of the fluid to be filtered is oriented in the direction of a lateral surface of the filter element in order to separate particles contained in the fluid onto a wall of the receiving section with the aid of centrifugal force.

CROSS-REFERENCE TO RELATED APPLICATIONS

The This application is a divisional of U.S. application Ser. No.15/095,127, filed 10 Apr. 2016, which claims the benefit of U.S.Provisional Application No. 62/186,576, filed 30 Jun. 2015. U.S.application Ser. No. 15/095,127 claims a priority date of 10 Apr. 2015based on prior filed German patent application No. 102015004383.8, theentire contents of the aforesaid US patent application, the USprovisional application and the aforesaid German patent applicationbeing incorporated herein by reference to the fullest extent permittedby the law.

TECHNICAL FIELD

The present invention relates to a filter holder, a filter element and afilter arrangement.

BACKGROUND

Known air filters for motor vehicles can have an annularly closed,radially folded filter medium that can be wound onto a center pipe, forexample. Particularly in the area of agricultural commercial vehiclesand construction vehicles, the filter medium can become clogged ordamaged due to the heavy dust load. This can reduce the service life andthe filtration efficiency of the air filter.

WO 2009/106591 A2 describes an air filter with a pre-separator. With theaid of the pre-separator, particles contained in the raw gas can beseparated off by means of centrifugal force. An increase in thefiltration efficiency can be achieved in this way, since the particlesare removed from the raw gas before reaching the air filter.

SUMMARY

Against this background, it is the object of the present invention toprovide an improved filter holder for a filter element.

Accordingly, a filter holder for a filter element is proposed that hasan oval-shaped cross section transverse to a longitudinal direction. Thefilter holder comprises a receiving section for receiving the filterelement, a fluid inlet for allowing fluid to be filtered into the filterholder, and a fluid outlet for letting the fluid filtered with the aidof the filter element out of the filter holder, the fluid inlet beingarranged such that an inflow direction of the fluid to be filtered isoriented in the direction of a lateral surface of the filter elementthat can be received in the receiving section or along an inner wall ofthe receiving section, particularly substantially orthogonally to thelongitudinal direction, whereby the fluid to be filtered flowstangentially and/or helically, particularly in the manner of anoval-shaped helix, around the filter element in order to separateparticles contained in the fluid to be filtered on a wall of thereceiving section with the aid of centrifugal force.

The filter holder can also be referred to as a housing or filterhousing. Due to the fact that the inflow direction is oriented in thedirection toward the filter element, the flow against the filter elementis direct in comparison to known arrangements. Since the filter holderitself acts as a pre-separator, particularly as a centrifugal separator,additional pre-separators arranged upstream from the filter element canbe omitted. This results in a cost advantage compared to knownarrangements. The particularly oval-shaped cross-sectional geometry ofthe receiving section leads to a favorable pre-separation efficiency ofthe particles in comparison to a circular cross-sectional geometry.Moreover, due to the oval-shaped cross-sectional geometry, narrow orrectangular installation spaces can also be used for receiving thefilter holder with the same structural volume. In particular, the filterholder is arranged such that a latitudinal direction of the receivingsection is positioned horizontally. Preferably, the inflow direction ofthe fluid to be filtered is oriented such that the fluid strikesdirectly on a region of more pronounced curvature of the wall of thereceiving section. As a result, the fluid is accelerated greatly. Thisleads to a favorable pre-separation efficiency in comparison to areceiving section with a circular cross section. The term “oval-shaped”can be understood here as a rectangular geometry with rounded-offcorners, an at least approximately elliptical geometry, or a geometryformed from several curved or circular sections. An oval shape with twoaxes of symmetry that intersect particularly orthogonally at a midpointthrough which a center axis of filter holder and/or filter element(s)runs perpendicular to the two axes of symmetry is preferred here bothfor the filter holder and for the filter elements and/or sealing devicethereof. Elliptical shapes can also be produced through approximatedconstructions of ellipses, such as by means of circles of curvature oraccording to Ia Hire, for example. Preferably, the receiving section hasa first and a second housing part that can be interconnected with theaid of fastening means. The housing parts can be made of a plasticmaterial. Preferably, the housing parts are plastic injection-moldedcomponents. Alternatively, the housing parts can also be made of sheetmetal. The receiving section can also be embodied as a single piece.That is, the housing parts can be integrally connected to one another.The particles can, for example, be sand, dust, plant parts or the like.

In embodiments, the inflow direction of the fluid to be filtered isoriented perpendicular to the longitudinal direction of the filterelement that can be received in the receiving section. As a result, thefluid to be filtered flows partially into the interspace betweenreceiving section and filter element and, optionally, at least partiallydirectly against the filter element as well, flowing around samepreferably helically.

In other embodiments, the receiving section is set up to receive thefilter element in the center of the receiving section with respect to alongitudinal direction of the filter element. A second end plate of thefilter element can have clamping elements that are elasticallydeformable in the longitudinal direction and with the aid of which thefilter element can be optimally positioned in the receiving section. Theelastically deformable clamping elements also serve to provide vibrationdamping and/or tolerance compensation.

In other embodiments, the receiving section is set up to receive thefilter element such that constant spacing is provided between the filterelement and the wall of the receiving section perpendicular to the outerlateral surface of the filter element and/or perpendicular to the innerwall of the receiving section circumferentially around the filterelement. The spacing is preferably substantially or completely constantover the longitudinal direction but can also vary in the longitudinaldirection. For example, the space can decrease or increase in thelongitudinal direction. The filter element can taper conically in thelongitudinal direction, for example, with or against the outflowdirection.

In other embodiments, the receiving section has a latitudinal directionand a vertical direction in cross section that preferably coincide withaxes of symmetry of the oval shape, the fluid inlet being arranged suchthat the inflow direction of the fluid is arranged perpendicular to thelatitudinal direction. Preferably, the fluid inlet is arranged laterallyon the receiving section such that the inflowing fluid strikes the wallof the receiving section.

In other embodiments, an extension of the receiving section in thelatitudinal direction is greater than in the vertical direction. Forexample, the receiving section is at least 1.5 times and preferably twoto three times wider than high. Preferably, the width-to-height ratio ofthe filter element to be received in the receiving section is greaterthan the width-to-height ratio of the receiving section. Morepreferably, a fitting filter element has such a similar height-to-widthratio and particularly a shape that is such that constant spacing isprovided between the filter element and the wall of the receivingsection perpendicular to the outer lateral surface of the filter elementand/or perpendicular to the inner wall of the receiving sectioncircumferentially around the filter element.

In other embodiments, the fluid inlet has an oval-shaped cross sectionwith a diameter that is greater parallel to the longitudinal axis of thefilter holder than perpendicular to the longitudinal axis. Low pressureloss during flowing of the fluid to be filtered into the fluid inlet canbe achieved in this way. Alternatively, the fluid inlet can have acircular cross section.

In other embodiments, the filter holder comprises a removablemaintenance cover having a particle discharge opening. The maintenancecover is preferably a plastic injection-molded component. Themaintenance cover can be made of a sheet metal. The maintenance covercan be attached to the receiving section using quick-action fasteners.The particle discharge opening can have a valve.

In other embodiments, the maintenance cover has a tubular, particularlyoval-shaped tubular incident-flow guard that particularly projects intothe interior of the filter holder and in which the filter element can bereceived at least partially and preferably coaxially. The incident-flowguard is preferably formed in a materially integral manner with themaintenance cover. The length of the incident-flow guard is preferablydesigned such that it surrounds the filter element over about 15-50%,preferably 20-40% of its total length in the longitudinal directionstarting from the closed end plate, that is, the length of theincident-flow guard in the longitudinal direction is about 15-50%,preferably 20-40% of the length of the filter element.

Furthermore, a filter element is proposed that has an oval-shaped crosssection transverse to a longitudinal direction thereof. The filterelement comprises a first end plate, a second end plate, and a filterbody arranged between the first end plate and the second end plate, itbeing possible for the filter element to have an incident-flow guardthat covers the filter body at least partially. The filter element canhave features named above and/or below or in the claims.

The incident-flow guard can also be provided on the receiving section.With the aid of the incident-flow guard, particles contained in thefluid to be filtered, such as sand, for example, are prevented fromstriking the filter medium directly. This prevents the filter mediumfrom being damaged. This increases the service life of the filterelement. The filter element is preferably an air filter for filteringintake air for a combustion engine. Preferably, the filter element isused in motor vehicles, trucks, construction vehicles, watercraft,railway vehicles, agricultural machines and vehicles or aircraft. Thefilter medium is preferably folded in a zigzag pattern. The filtermedium is a filter paper, a filter fabric, a filter roving or a nonwovenfilter web, for example. Particularly, the filter medium can bemanufactured using a spunbonded or meltblown process. Moreover, thefilter medium can be felted or needled. The filter medium can havenatural fibers, such as cellulose or cotton, or synthetic fibers, suchas polyvinyl sulfite or polytetrafluoroethylene. The fibers can beoriented obliquely and/or transverse to the machine direction duringprocessing, or they can be unordered. The filter medium can be fusedwith or adhered or welded to the end plates.

In embodiments, the incident-flow guard is adhered or welded to or fusedwith the filter body formed from the filter medium. Alternatively, theincident-flow guard lies flush and preferably loosely on the filtermedium, particularly the folding edges of the filter medium. Inparticular, the incident-flow guard is arranged adjacent to a first endplate of the filter element. The incident-flow guard can be connected tothe first end plate, for example enclosed by its material in a partiallyform-fitting manner.

In other embodiments, the incident-flow guard is fluid-tight. Theincident-flow guard can be a film. Alternatively, the incident-flowguard can be fluid-permeable. For example, the incident-flow guard canbe made of a fine-mesh net or lattice. Preferably, the incident-flowguard is made of a plastic material.

In other embodiments, the filter element surrounds a secondary element,which can also be received in the filter holder. The filter element canalso be referred to as the first filter element and the secondaryelement as the second filter element. The first end plate of the filterelement preferably has a receiving opening into which the secondaryelement can be pushed. At the same time, this receiving openingpreferably represents the outflow cross section of the first filterelement.

In other embodiments, the filter element has a sealing device providedon the preferably open first end plate, the sealing device being set upto seal the filter element particularly radially or axially with respectto a filter holder such that the inflow side or unfiltered side of thefilter element is separated from the outflow side or filtered side.Preferably, the sealing device is embodied in a materially integralmanner with the first end plate. Particularly, the first end plate andthe sealing device can be made from a particularly cast polyurethanematerial, particularly a foamed polyurethane material. The sealingdevice can preferably be deformed in a spring-biased manner. The sealingdevice is preferably set up so as to seal the filter element radiallyinward with respect to the filter holder, i.e., in the direction towarda fluid outlet of the filter holder and preferably has an inwardlyaligned, annularly closed, particularly oval-shaped sealing surface forthis purpose. The sealing device can also be set up for the purpose ofsealing the filter element axially with respect to the filter holder.

Moreover, a filter arrangement with such a filter holder and such afilter element received in a receiving section of the filter holder isproposed, a fluid inlet of the filter holder being arranged such that aninflow direction of the fluid to be filtered is oriented in thedirection of a lateral surface of the filter element received in thereceiving section such that the fluid to be filtered flows tangentiallyand/or helically, particularly in the manner of an oval-shaped helix,around the filter element received in the receiving section in order toseparate particles contained in the fluid to be filtered on a wall ofthe receiving section with the aid of centrifugal force.

Preferably, the inflow direction of the fluid to be filtered is orientedsuch that the fluid strikes directly on a curvature of the wall of thereceiving section. As a result, the fluid is accelerated greatly,whereby the centrifugal forces acting on the fluid are increased. Thispromotes the particle pre-separation efficiency. The filter arrangementcan also be referred to as a two-stage filter, the first stage beingconstituted by the centrifugal separation and the second stage by afilter element.

Moreover, a filter element having an oval-shaped cross section in alongitudinal direction thereof is proposed that can preferably be usedparticularly in a filter holder according to the invention.

The filter element comprises a circumferential sealing device forsealing the filter element particularly radially with respect to afilter holder for the filter element, the sealing device having twofirst curved sections arranged opposite one another and two secondcurved sections arranged opposite one another, the first curved sectionseach having a first radius of curvature and the second curved sectionseach having a second radius of curvature, the first radius of curvaturediffering from the second radius of curvature. One construction of theseal exclusively with two different radii, each of which is completelyor at least substantially constant over the individual curved sections,can have advantages with respect to tool manufacturing and qualitycontrol.

The second radius of curvature can approach infinite, that is, it canalso be straight, which also applies analogously to an oval shape of thefilter element. In one embodiment, the sealing device has asubstantially stadium-like geometry. It has also proven advantageous forthe sealing device to have no straight sections, but rather only curvedsections. This is particularly evident if the filter element and/or thefilter body formed from a filter medium has an oval-shaped cross sectionwhose outer contour has partially straight or slightly curved sections.By virtue of the fact that the sealing device has substantiallyexclusively curved sections, constant contact pressure of the sealingdevice against an engagement area of the filter holder can be achievedover the entire periphery of the sealing device. The sealing device ispreferably set up for the purpose of sealing the filter element radiallyinward with respect to the filter holder. More pronounced curvatures orsmaller radii on the sealing device are more advantageous when forming aseal radially inward or outward than less pronounced curvatures orlarger radii, since, as the curvature increases, the danger of thesealing device losing contact with a seal contact surface on the filterholder side under a vibrational load decreases. Alternatively or inaddition, the sealing device can also be set up for the purpose ofsealing the filter element axially with respect to the filter holder.The term “inward” is to be understood herein as a direction orientedradially toward a fluid outlet of the filter holder. The sealing devicecan preferably be deformed in a spring-biased manner. The filter elementcan spatially surround a secondary element. The sealing devicepreferably runs completely around a first end plate of the filterelement. The filter element is preferably an air filter for filteringintake air for a combustion engine. Preferably, the filter element isused in motor vehicles, trucks, construction vehicles, watercraft,railway vehicles, agricultural machines and vehicles or aircraft.

According to the idea of the invention, it is advantageous but notabsolutely necessary to select a profile for the sealing device that isparticularly formed exclusively of circular sections. One substantialadvantage lies namely in the fact that the sealing device has onlycurved sections, particularly is continuously curved in one direction,thus creating a continuously convex outer contour or straight or concavesections. The invention therefore relates more generally to a filterelement as well having an oval-shaped cross section defined by a filterbody of a filter medium with two first opposing curved sections with amore pronounced curvature that are interconnected by two opposing curvedsections with a less pronounced curvature compared to the first curvedsections, the filter element further including an oval-shapedcircumferential sealing device particularly for sealing the filterelement radially with respect to a filter holder, the sealing devicehaving two mutually opposed first curved sections with a more pronouncedcurvature and two curved sections with a less pronounced curvaturecompared to the first curved sections, the second curved sections of thesealing device having a more pronounced curvature than the second curvedsections of the oval-shaped cross section defined by the filter body.The first curved sections are preferably interconnected by the secondcurved sections such that first and second curved sections transitionrespectively into one another, particularly transition directly into oneanother, preferably constantly and more preferably smoothly. Oneconsequence of this, for example, is that, in the transition portionbetween first and second curved sections, no additional curved sectioncan be present with a curvature that is greater than the curvature ofthe first two curved sections. This offers the advantage that, despitethe non-circular shape, a good circumferential sealing effect can beensured.

Preferably, an oval-shaped cross section or profile is selected for thesealing device and/or the filter body and/or at least one of the endplates that has a midpoint and two axes of symmetry intersectingtherewith and/or a width-to-height ratio of greater than 1.5:1,preferably greater than 2:1, more preferably less than 5:1 or 4:1,especially preferably less than 3:1. Width-to-height ratios of thefilter element and/or filter body in the range between 1.5:1 and 3:1 areespecially advantageous for a pre-separation effect by centrifugalforce. Especially preferably, filter body and sealing device have thesame axes of symmetry. Especially preferably, the filter element has alongitudinal axis of symmetry to which the sealing device and/or thefilter body and/or at least one end plate are at least substantiallysymmetrical. This longitudinal axis of symmetry preferably runs throughthe point of intersection of the abovementioned intersecting axes ofsymmetry, preferably perpendicularly thereto in each case. Thelongitudinal axis of symmetry is preferably coaxial with the center axisof filter holder and/or filter element or can be defined by them.

It is especially preferred in all embodiments that the second curvedsections of the sealing device and the second curved sections of theoval-shaped cross section defined by the filter body are arrangedadjacent to one another, that is, they have substantially the sameangular position with respect to the oval shape. The same applies to thefirst curved section of the sealing device that has a more pronouncedcurvature than the second, and to the cross section defined by thefilter body.

In embodiments, curvature midpoints of the first radii of curvature arearranged on a first line and the curvature midpoints of the second radiiof curvature are arranged on a second line, the first line beingpositioned perpendicular to the second line. Preferably, the secondradii of curvature are greater than the first radii of curvature. Thefirst radii of curvature are preferably of equal size. The second radiiof curvature are preferably of equal size.

In other embodiments, the second line is arranged in the center betweenthe curvature midpoints of the first radii of curvature and/or the firstline is arranged in the center between the curvature midpoints of thesecond radii of curvature. The end points of the line are respectivelydefined by the curvature midpoints. Preferably, the first line bisectsthe second line and vice versa.

A filter element according to the invention preferably has a filter bodyformed from a filter medium. The filter body can preferably be flowedthrough radially from the outside or vice versa. The filter body canpreferably be formed by an annularly closed filter medium that is foldedin a zigzag pattern and have a circular, oval or elliptical shape.Furthermore, the filter body can be formed from a tubular, particularlymultilayered winding of a filter medium. Alternatively, the filter bodycan be embodied as a filter body that can be flowed through axially, forexample through a particularly oval-shaped winding of a semi-finishedproduct with two layers of filter medium, a corrugated layer, and asmooth layer that form mutually sealed channels.

In other embodiments, the filter element has at least one end plate anda filter body connected to the end plate, the sealing device beingprovided on a front side of the particularly open end plate facing awayfrom the filter body. The end plate is preferably a first end plate ofthe filter element. Preferably, the filter element has two end platesbetween which the filter body is arranged. The sealing device can beembodied in a materially integral manner with the first end plate. Thesecond end plate can preferably be closed.

In other embodiments, an outer contour and/or inner contour of thesealing device is not arranged parallel to an outer contour and/or innercontour of the end plate. Preferably, the outer or inner contour of thesealing device does not follow the outer or inner contour of the endplate, that is, the distance of the outer contour of the sealing devicefrom the outer contour of the end plate is not constant. Morepreferably, the sealing surface, i.e., the contact surface of thesealing device that rests in a sealing manner against a correspondingseal contact surface of the housing, does not follow the outer contourof the end plate. In the case of a radial seal, this generally appliesto the radial inner surface of the sealing device, but the radial outersurface of the sealing device can also form the sealing surface.Especially preferably, the sealing device, particularly the innersurface of the seal, is nearer to the outer (particularly radiallyouter) lateral surface of the filter body and/or the outer contour of anopen end plate in the center of the curved sections of the filter bodyand/or of the sealing device with lesser curvature than in thetransitional portion between curved sections of the filter body and/orsealing device with pronounced and non-pronounced curvature. In thisway, the curvature of the seal in the slightly curved region of thefilter body can be reinforced and thus optimized with respect to thereliability of the seal under a vibrational load. Geometricallyspeaking, this preferably results in the curvature of the second curvedsections of the seal not being constructable even by means of a scaleenlargement/reduction (central stretching) of the outer contour of theopen end plate and/or of the filter body. Rather, this preferably meansthat the curvature of the second curved sections of the seal is morepronounced than the curvature of a comparable, particularly concentriccurve that is particularly parallel to the outer contour of filter bodyand/or open end plate, particularly obtained from the outer contourthrough scale reduction or within the outer contour and running parallelthereto that is at least substantially the same distance to the outercontour of end plate and/or filter body in the center of the secondcurved sections of seal, outer contour of the end plate and/or outercontour of the filter body. In an advantageous embodiment, the sealingdevice is arranged within an imaginary axial continuation of the outerlateral surface of the filter body and/or of the outer contour of anopen end plate in the longitudinal direction. This offers the advantagethat the sealing device does not require any additional installationspace radially to the longitudinal direction and can be embodieddirectly, for example integrally with or in the same material as the endplate. If an annularly closed filter bellows made of a filter mediumfolded in a zigzag or radial manner is used, it can be especiallyadvantageous for the sealing device to be arranged within a crosssection of the filter body (more specifically within an imaginary axialcontinuation of the cross section in the longitudinal direction). Thisoffers the advantage that the cross section of the outflow path from thefilter element is not unnecessarily reduced by the sealing device, whichwould increase the flow resistance.

In other embodiments, the filter element has an incident-flow guard thatencloses the filter body at least in sections. With the aid of theincident-flow guard, particles contained in the fluid to be filtered,such as small stones, for example, are prevented from striking thefilter medium directly. This prevents the filter medium from beingdamaged. This increases the service life of the filter element.

In other embodiments, the incident-flow guard is adhered, welded orfused to the filter body. Alternatively, the incident-flow guard liesflush and preferably loosely on the filter medium, particularly thefolding edges of the filter medium. In particular, the incident-flowguard is arranged adjacent to a first end plate of the filter element.The incident-flow guard can be connected to the first end plate, forexample enclosed by its material in a partially form-fitting manner. Asa result, the incident-flow guard can be permanently connected to thefilter body by means of the end plate material, particularlypolyurethane or polyurethane foam.

In other embodiments, the incident-flow guard is fluid-tight. Theincident-flow guard can be a film. Alternatively, the incident-flowguard can be fluid-permeable. For example, the incident-flow guard canbe made of a fine-mesh net or lattice. Preferably, the incident-flowguard is made of a plastic material.

The incident-flow guard runs preferably once completely, particularly inan annularly closed manner, around the filter body. In this way, it canbe ensured that a filter element that can be installed in two positionsdue to symmetry is protected in both positions from frontal flow througha fluid inlet and/or that the formation of the unfiltered fluid flowrotating around the filter element that is important for thepre-separation is ensured in like manner in both installation positions.The incident-flow guard should preferably extend over the entireperiphery, or at least axially from the first end plate so far over thefilter body in the regions that may be subjected to direct flow that theaxial extension of the fluid inlet of a filter housing is covered.Depending on the design of the filter system, this is the case if theincident-flow guard extends over at least 15, 20 or 25% of the axiallength of the filter body and/or a maximum of 80, 70, 60, 50, 40 or 30%of the axial length of the filter body.

Moreover, a filter arrangement with such a filter holder and such afilter element is proposed that is received in a receiving section ofthe filter holder.

In embodiments, the receiving section has an engagement area into whicha circumferential sealing device of the filter element engages, thesealing device abutting with an inner surface against the engagementarea. The engagement area is preferably provided circumferentiallyaround a fluid outlet of the filter holder. The sealing devicepreferably abuts on the inside against the engagement area.

Moreover, a filter holder particularly for a filter element according tothe invention is proposed that has an oval-shaped cross sectiontransverse to a longitudinal direction thereof. The filter holdercomprises a receiving section for receiving the filter element, a fluidinlet for allowing fluid to be filtered into the filter holder, and afluid outlet for letting the fluid filtered with the aid of the filterelement out of the filter holder, the fluid inlet being arranged suchthat an inflow direction of the fluid to be filtered into the fluidinlet is oriented parallel to the longitudinal direction of the filterelement, the fluid inlet having a guide member that is set up for thepurpose of deflecting the fluid to be filtered upon flowing into thefluid inlet such that it flows in a helical manner around the filterelement that can be received in the receiving section in order toseparate particles contained in the fluid to be filtered on a wall ofthe receiving section with the aid of centrifugal force. The guidemember can be a guide vane. By virtue of the fact that the fluid to befiltered flows around the filter element in the manner of a spiral,screw or helix, the filter holder acts as a pre-separator for separatingthe particles. Additional pre-separators can thus be omitted. As aresult, the filter holder can be especially cost-effective tomanufacture. The filter holder preferably has an oval-shaped crosssection. The preferably oval-shaped cross-sectional geometry of thereceiving section leads to a favorable pre-separation efficiency of theparticles in comparison to a circular cross-sectional geometry.Moreover, due to the oval-shaped cross-sectional geometry, narrow orrectangular installation spaces can also be used for receiving thefilter holder. In particular, the filter holder is arranged such that alatitudinal direction of the receiving section is positionedhorizontally. Preferably, the receiving section has a first and a secondhousing part that can be interconnected with the aid of fastening means.The housing parts can be made of a plastic material or of a metallicmaterial. Preferably, the housing parts are plastic injection-moldedcomponents. The receiving section can also be embodied as a singlepiece. That is, the housing parts form a component. Preferably, themaintenance cover can be removed from the receiving section. Inembodiments, the filter holder has a plurality of fluid inlets. Eachfluid inlet has at least one guide member. The guide members arepreferably embodied as guide vanes. In other embodiments, the fluidinlets are arranged uniformly over the periphery of the filter holder.Preferably, the fluid inlets are arranged so as to be uniformlyspaced-apart from one another. Alternatively, the fluid inlets can bearranged in an irregular manner. In other embodiments, a respectiveangle of curvature of the guide members changes over a periphery of thefilter holder. Each guide member preferably has a first section orientedparallel to the inflow direction and a second section oriented obliquelyto the inflow direction. The sections are arranged so as to tiltrelative to one another in the angle of curvature. The angles ofcurvature of all guide members can be equal.

Alternatively, the guide members can have different angles of curvature.For example, the angles of curvature can vary over a periphery of thefilter holder.

In other embodiments, a respective inflow cross section of the fluidinlets changes over a periphery of the filter holder. The inflow crosssection can be rectangular or round, for example. The pre-separationefficiency can be optimized by varying the inflow cross sections.

In other embodiments, the fluid inlet is arranged on a maintenance coverthat can be removed from the filter holder. Preferably, the fluid inletis an opening in the maintenance cover. The maintenance cover preferablyalso has the guide members. The guide members are particularly formed ina materially integral manner with the maintenance cover. The maintenancecover can be attached to the filter holder with the aid of quick-actionfasteners.

In other embodiments, the guide member is positioned such that it isarranged next to same in the longitudinal direction of the filterelement. Preferably, a plurality of guide members is arranged around thefilter element. As a result, the installation space available for thefilter holder can be optimally exploited by the filter element. Thelength of the filter element can thus correspond approximately to thelength of the filter holder. In other embodiments, the filter holder hasa tubular incident-flow guard in which the filter element can bearranged at least partially. The incident-flow guard or theincident-flow edge is preferably fluid-tight.

In other embodiments, the incident-flow guard is embodied in amaterially integral manner with a maintenance cover of the filter holderand/or with the filter holder. The maintenance cover is preferably acost-effective plastic injection-molded component. The maintenance covercan be made of sheet metal.

Moreover, a filter arrangement with such a filter holder and a filterelement that is received in a receiving section of the filter holder isproposed.

Moreover, a filter holder particularly for a filter element according tothe invention is proposed that has an oval-shaped cross sectiontransverse to a longitudinal direction thereof. The filter holdercomprises a receiving section for receiving the filter element, a fluidinlet for letting in fluid to be filtered into the filter holder, and afluid outlet for letting the fluid filtered with the aid of the filterelement out of the filter holder, the fluid outlet being arranged suchthat an outflow direction of the filtered fluid from the fluid outlet isoriented parallel to the longitudinal direction of the filter element,and the fluid outlet having a circular cross section facing away fromthe fluid outlet and an oval-shaped cross section facing toward thefilter element.

As a result, the pressure loss as the filtered fluid flows out isreduced. This increases the efficiency of a filter arrangement with sucha filter holder. Preferably, the height of the oval-shaped cross sectionis smaller than the diameter of the circular cross section. Inembodiments, the circular cross section and the oval-shaped crosssection of the fluid outlet have the same cross-sectional surface area.As a result, the filtered fluid can flow off unimpeded. The oval-shapedcross section can also have a larger cross-sectional surface area thanthe circular cross section.

In other embodiments, the fluid outlet has a curved transitional sectionthat connects the circular cross section of the fluid outlet to theoval-shaped cross section of the fluid outlet. The transitional crosssection is preferably curved in an S-shape.

In other embodiments, the fluid inlet widens in a latitudinal directionof the filter element from the circular cross section to the oval-shapedcross section. Preferably, a width of the oval-shaped cross section isgreater than a diameter of the circular cross section. In otherembodiments, the fluid inlet narrows in a vertical direction of thefilter element from the circular cross section to the oval-shaped crosssection. Preferably, a height of the oval-shaped cross section issmaller than a diameter of the circular cross section. In otherembodiments, the filter holder has a tubular incident-flow guard inwhich the filter element can be received at least partially. Theincident-flow guard or the incident-flow edge is preferably fluid-tight.

In other embodiments, the incident-flow guard is embodied integrallywith a maintenance cover that can be removed from the filter holder. Themaintenance cover is preferably a cost-effective plasticinjection-molded component. Alternatively, the maintenance cover can bemade of sheet metal, particularly sheet steel.

Furthermore, a filter element is proposed that has an oval-shaped crosssection transverse to a longitudinal direction thereof. The filterelement comprises a first end plate, a second end plate, and a filterbody arranged between the first end plate and the second end plate, across section of the filter body on the second end plate being greaterthan a cross section of the filter medium on the first end plate. Thefilter element can have one or more of the features described above orbelow or in the claims. Preferably, the filter body tapers conically onthe inside. This enables an enlarged fluid outlet opening of the filterelement in comparison to a filter body that does not taper conically.The transitional section of the fluid outlet can hereby be optimized,since the height of the oval-shaped cross section of the fluid outletcan approach the diameter of the circular cross section of the fluidoutlet. This leads to further reduced pressure loss. The filter elementis preferably an air filter element for filtering intake air for acombustion engine. Preferably, the filter element is used in motorvehicles, trucks, construction vehicles, watercraft, railway vehicles,agricultural machines and vehicles or aircraft.

In embodiments, the cross section of the filter body enlargescontinually from the first end plate in the direction toward the secondend plate. The filter element can surround a secondary element that canbe received in the filter holder. The secondary element can have aconical or frustoconical geometry corresponding to the filter body ofthe first filter element.

Moreover, a filter arrangement with such a filter holder and such afilter element and/or secondary element is proposed that is received ina receiving section of the filter holder. Other possible implementationsof the invention also comprise combinations of features or method stepsthat were not explicitly mentioned previously or that are describedbelow in relation to the exemplary embodiments. A person skilled in theart will also add individual aspects to the respective basic form of theinvention as improvements or supplementations.

Other embodiments of the invention are the subject of the subclaims andof the exemplary embodiments of the invention described below. Theinvention will be explained in further detail below on the basis ofexemplary embodiments with reference to the enclosed figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic, perspective view of an embodiment of a filterarrangement;

FIG. 2 shows a schematic view of the filter arrangement according toFIG. 1 ;

FIG. 3 shows a schematic view of the filter arrangement according toFIG. 1 ;

FIG. 4 shows a partial sectional view of the filter arrangementaccording to FIG. 1 ;

FIG. 5 shows a partial sectional view of the filter arrangementaccording to FIG. 1 ;

FIG. 6 shows a schematic, perspective view of an embodiment of a filterelement;

FIG. 7 shows a schematic, perspective view of an embodiment of asecondary element;

FIG. 8 shows a schematic view of the filter arrangement according toFIG. 1 ;

FIG. 9 shows a schematic sectional view of the filter arrangementaccording to sectional line IX-IX of FIG. 8 ;

FIG. 10 shows a schematic sectional view of the filter arrangementaccording to sectional line X-X of FIG. 8 ;

FIG. 11 shows a schematic partial sectional view of the filterarrangement according to FIG. 1 ;

FIG. 12 shows a schematic, perspective view of another embodiment of afilter arrangement;

FIG. 13 shows a schematic, perspective view of another embodiment of afilter arrangement;

FIG. 14 shows a schematic, perspective view of another embodiment of afilter element;

FIG. 15 shows a schematic sectional view of the filter arrangementaccording to FIG. 14 ;

FIG. 16 shows a schematic view of the filter arrangement according toFIG. 14 ;

FIG. 17 shows a schematic partial sectional view of the filterarrangement according to FIG. 14 ;

FIG. 18 shows a schematic, partial sectional view of another embodimentof a filter element;

FIG. 19 shows a schematic, partial sectional view of another embodimentof a filter arrangement;

FIG. 20 shows a schematic, perspective view of another embodiment of afilter arrangement;

FIG. 21 shows a schematic, perspective partial sectional view of thefilter arrangement according to FIG. 20 ;

FIG. 22 shows a schematic partial sectional view of the filterarrangement according to FIG. 20 ;

FIG. 23 shows a schematic sectional view of the filter arrangementaccording to FIG. 20 ;

FIG. 24 shows a schematic partial sectional view of the filterarrangement according to FIG. 20 ;

FIG. 25 shows a schematic view of the filter arrangement according toFIG. 20 ;

FIG. 26 shows a schematic, perspective view of another embodiment of afilter arrangement;

FIG. 27 shows a schematic view of the filter arrangement according toFIG. 26 ;

FIG. 28 shows a schematic sectional view of the filter arrangementaccording to FIG. 26 ;

FIG. 29 shows a schematic sectional view of the filter arrangementaccording to FIG. 26 ;

FIG. 30 shows a schematic sectional view of the filter arrangementaccording to FIG. 26 ;

FIG. 31 shows a schematic sectional view of the filter arrangementaccording to FIG. 26 ; and

FIG. 32 shows a schematic partial sectional view of the embodiment of afilter arrangement according to FIG. 19 in which the filter element isnot shown.

In the figures, same or functionally equivalent elements have beenprovided with the same reference symbols unless indicated otherwise.

DETAILED DESCRIPTION

FIG. 1 shows a schematic, perspective view of an embodiment of a filterarrangement 1. FIG. 2 shows a front view of the filter arrangement 1.FIG. 3 shows a side view of the filter arrangement 1. FIG. 4 and FIG. 5each show partial sectional views of the filter arrangement 1.

The filter arrangement 1 comprises a filter holder 2 and a filterelement 3 arranged in the filter holder 2. The filter holder 2 can alsobe referred to as a housing or filter housing. The filter element 3 isshown in FIG. 6 . The filter arrangement 1 is preferably used as anintake air filter for combustion engines, for example in motor vehicles,trucks, construction vehicles, watercraft, railway vehicles,agricultural machines and vehicles or aircraft. The filter element 3 isparticularly suited to filtering combustion air of a combustion engine.Preferably, the filter element 3 is an air filter element.

The filter element 3, which can also be referred to as a primary elementor main element, comprises a filter body 4 that surrounds a center tube5 and preferably abuts against same such that the center tube 5 cancarry out a support function for the filter body when it is being flowedthrough. For example, the filter body 4 can be wound onto the centertube 5 as a winding of a filter medium, or it can be closed on same inthe manner of a ring, for example in the form of a radially foldedbellows. The center tube 5 is preferably lattice-shaped and thuspermeable to fluids. The filter body 4 is preferably folded. Forstabilization, the folded filter medium can be wrapped around with ayarn winding package 6, i.e., a strap or yarn that is soaked in ahot-melt adhesive or other adhesive, or it can be fixed by means ofadhesive beads running circumferentially in a circular or spiral shape.The filter medium is a filter paper, a filter fabric, filter roving or anonwoven filter web, for example. Particularly, the filter medium can bemanufactured in a spunbonding or meltblown process or comprise such alayer of fibers applied to a nonwoven or cellulose substrate. Moreover,the filter medium can be felted or needled. The filter medium can havenatural fibers, such as cellulose or cotton, or synthetic fibers, suchas polyvinyl sulfite or polytetrafluoroethylene. The fibers can beoriented obliquely and/or transverse to the machine direction duringprocessing, or they can be unordered.

The filter element 3 has a first, particularly open end plate 7 and asecond, particularly closed end plate 8. The end plates 7, 8 arepreferably made of a plastic material. For example, the end plates 7, 8can be embodied as cost-effective plastic injection-molded components.The end plates 7, 8 can, for example, be made of a polyurethane materialthat is particularly cast, preferably foamed in casting shells. The endplates 7, 8 can be cast against the filter body 4. The filter body 4 isarranged between the end plates 7, 8. A sealing device 10 for sealingthe filter element 3 with respect to the filter holder 2 is provided ona front side 9 of the first end plate 7 facing away from the filter body4. The sealing device 10 is set up for the purpose of sealing the filterelement 3, particularly radially, with respect to the filter holder 2.

The filter medium of the filter body 4 can be fused with or adhered orwelded to the end plates 7, 8. The second end plate 8 is disc-shaped,for example, and preferably impermeable to fluids. A receiving opening11 is provided in the first end plate 7 through which the air filteredby the filter element 3 can continue to exit. Moreover, the filterelement 3 preferably has an incident-flow guard 12 that preventsparticle-laden fluid L from flowing directly against the filter medium4. The fluid L can be air. The incident-flow guard 12 can be a film or aclose-meshed net or screen. The incident-flow guard 12 can beimpermeable to fluids or permeable to fluids. The incident-flow guard 12can be adhered, welded or fused to the filter body 4. The incident-flowguard 12 is arranged adjacent to the first end plate 7. In particular,the incident-flow guard 12 adjoins the first end plate 7. Theincident-flow guard 12 can be connected, particularly in a flow-tightmanner, to the first end plate 7. Fluid L to be cleaned emerges from anunfiltered side RO of the filter element 3 through the filter body 4into a cavity surrounded by a center tube 5 and flows out of that asfiltered fluid through the receiving opening 11 to a filtered side RL ofthe filter element 3 particularly surrounded by the filter body 4.

The filter element 3 preferably has an oval-shaped cross section in alongitudinal direction LR thereof. The cross section can decreasestarting from the first end plate 7 in the direction of the second endplate 8, so that the filter element 3 tapers conically. Preferably,however, the filter element 3 has an oval-shaped cross section, as shownin FIG. 6 . That is, the filter element 3 is cylindrical with anoval-shaped base surface. In the present document, the term “oval” canbe understood as being a shape with a non-concave, smooth outer contour,i.e., that is formed continuously from convex and straight sections,preferably exclusively from convex sections, for example a rectangularcross section with rounded-off corners, an elliptical cross section, ora cross section formed from several circular arcs. Preferably, anoval-shaped outer contour or a cross section is used that has a midpointand two axes of symmetry intersecting at said midpoint. The filterelement 3 and particularly the filter body 4 have a width b and a heighth (FIG. 10 ). The width b is greater than the height h. Preferably, thewidth b is two to three times the height h; more preferably, the width bis 1.5 to three times the height h.

A secondary element 13, shown in FIG. 7 , can be received in the filterholder 2 surrounded by the filter element 3. Such secondary elementsserve particularly as security for cases in which an operator opens thefilter holder 2 and removes the filter element 3 while the machine isrunning, for example in order to remove dust or to change it.Particularly, the filter element 3 can also be referred to as the firstfilter element and the secondary element 13 as the second filterelement. Preferably, the secondary element 13 is received in thereceiving opening 11. The secondary element 13 has a filter medium 14 aswell as a first end plate 15 and a second end plate 16. The filtermedium 14 is arranged between the end plates 15, 16. The filter medium14 surrounds a lattice-like center tube 17. Like the filter element 3,the secondary element 13 has an unfiltered side RO and a filtered sideRL. The first end plate 15 can have a sealing device 18 for sealing thesecondary element 13 with respect to the filter holder 2. The sealingdevice 18 can be embodied in a materially integral manner with the firstend plate 15. The filter element 3 and the secondary element 13 can bereceived in the filter holder 2. The secondary element 13 has a fluidoutflow opening 51. The fluid outflow opening 51 can also be referred toas a fluid outflow opening of the filter element 3.

As can be seen in FIGS. 1 to 5 , the filter holder 2 comprises areceiving section 19. The receiving section 19 can be formed from afirst housing part 20 and a second housing part 21. The housing parts20, 21 can be interconnected using fastening means 22, such as screws,for example. The housing parts 20, 21 are preferably made of a plasticmaterial. Alternatively, the housing parts 20, 21 can be made of sheetmetal, particularly sheet steel. For example, the housing parts 20, 21can be embodied as cost-effective injection-molded components. A sealingdevice, such as an O-ring, for example, can be provided between thehousing parts 20, 21. Alternatively, the receiving section 19 can beembodied in a single piece. That is, the housing parts 20, 21 form aone-piece component.

Moreover, the filter holder 2 has a maintenance cover 23 that can beremoved from the receiving section 19. The filter element 3 can beremoved from the receiving section 19 via the maintenance cover 23. Themaintenance cover 23 can be attached to the receiving section 19 withthe aid of quick-action fasteners. A sealing device can be providedbetween the maintenance cover 23 and the receiving section 19. FIG. 2and FIG. 3 show the filter arrangement 1 in two different installationsituations, namely in a lying and in a standing orientation.

The filter holder 2 or the receiving section 19 has a fluid inlet 24 forletting the fluid L to be filtered into the filter holder 2 and aparticularly central fluid outlet 25 for letting the fluid L filteredwith the aid of the filter element 3 out of the filter holder 2. Thefluid inlet 24 and the fluid outlet 25 are preferably tubular. The fluidinlet 24 can have an oval-shaped cross section, as shown in FIGS. 1, 3and 4 . With the aid of the oval-shaped cross section, whose extensionis preferably oriented in the direction toward the longitudinaldirection LR, lower initial pressure loss can be achieved in comparisonto a circular cross section. The fluid L to be filtered enters the fluidinlet 24 in an inflow direction E. The fluid outlet 25 preferably has acircular cross section. The fluid L preferably emerges from the fluidoutlet 25 in an outflow direction A, preferably parallel to thelongitudinal direction LR of the filter element 3. The inflow directionE is oriented perpendicular to the outflow direction A.

A particle discharge opening 26 can be provided on the maintenance cover23. The particle discharge opening 26 is preferably tubular. Particlesthat are pre-separated from the fluid L can be discharged from thefilter holder 2 via the particle discharge opening 26. The particledischarge opening 26 can have a valve. The housing parts 20, 21 and/orthe maintenance cover 23 can be reinforced with ribs.

A first engagement area 27 (FIG. 5 ) is provided in the filter holder 2and particularly in the receiving section 19 into which the sealingdevice 10 of the filter element 3 engages. This engagement area 27preferably has a seal contact surface against which the sealing device10 can come to rest in a sealing manner. In the present exemplaryembodiment, an oval-cylindrical seal contact surface that is orientedradially outward and follows the profile of the inner surface 43(sealing surface) of the sealing device 10 is preferably provided asshown. Moreover, a second engagement area 28 can be provided in thereceiving section 19 into which the sealing device 18 of the secondaryelement 13 engages. This second engagement area 28 preferably also has aseal contact surface 280 (see FIG. 32 ) against which the sealing device18 can come to rest in a sealing manner. In the present exemplaryembodiment, an oval-cylindrical seal contact surface 280 that isoriented radially outward is preferably provided as shown. The firsthousing part 20 can have the engagement areas 27, 28. The engagementareas 27, 28 can run completely around the fluid outlet 25.

FIG. 8 shows the filter arrangement 1 in a schematic side view. As FIG.9 shows in a schematic sectional view along the sectional line IX-IX ofFIG. 8 , the fluid inlet 24 is arranged such that the inflow direction Eof the fluid L is oriented in the direction of a lateral surface 29 andperpendicular to the longitudinal direction LR of the filter element 3arranged in the receiving section 19. The lateral surface 29 forms anencasement end of the filter body 4. A cylindrical, particularlyoval-cylindrical geometry of the filter element 3 is formed by the endplates 7, 8 and the lateral surface 29. The fluid L to be filtered flowsaround the filter element 3 that can be received in the receivingsection 19 such that particles contained in the fluid L to be filteredcan be removed at a wall 30 of the filter holder 2 or of the receivingsection 19 with the aid of centrifugal force. The receiving section 19thus acts as a centrifugal separator. Particularly, the inflow directionE is oriented such that the fluid L to be filtered flows against thefilter element 3 in a substantially tangential manner. The receivingsection 19 preferably has a latitudinal direction br and a verticaldirection hr. The width-to-height ratio br/hr is preferably at least4:3, more preferably at least 3:2, particularly at least 2:1, and/or atmost 6:1, preferably at most 4:1, especially preferably at most 3:1 or2:1. For the purpose of optimized pre-separation, ratios of less than3:1 and preferably less than 2:1 or even less than 1.5:1 areadvantageous. Preferably, the fluid inlet 24 is arranged such that theinflow direction E is oriented perpendicular to the latitudinaldirection br, i.e., preferably perpendicular to the direction of thebroader extension.

As a result of the fact that the fluid inlet 24 is oriented such thatthe inflowing fluid L strikes a relatively more pronouncedly curvedcurvature 50 of the wall 30 of the receiving section 19, the fluid L tobe filtered is greatly accelerated and then flows around the filterelement 3 tangentially and particularly in the manner of a screw, spiralor helix. As a result, good particle separation from the fluid L isachieved. The fluid inlet 24 can be shielded with the aid of a wall 31from the fluid L flowing around the filter element 3, which supports theformation of a helical flow. The separated particles are removed fromthe receiving section 19 with the aid of the particle discharge opening26. The receiving section 19 runs in the longitudinal direction LR ofthe filter element 3 parallel to the lateral surface 29 of the filterelement 3 so that, as shown in FIG. 10 , a constant distance a isprovided between the filter element 3 and the wall 30 perpendicular tothe longitudinal direction LR around the filter element 3.

FIG. 11 shows a partial sectional view of the filter arrangement 1. Thefluid L to be filtered flows through the fluid inlet 24 into thereceiving section 19. As a result of the fact that the inflow directionE of the fluid L to be filtered is oriented in the direction of thelateral surface 29 of the filter element 3 and is particularly alsopositioned perpendicular to the longitudinal direction LR, the fluid Lto be filtered flows, as shown in FIG. 11 with the aid of an arrow 32,helically around the filter element 3 and through the filter body 4 ofthe filter element 3 in order to flow again as a filtered fluid L out ofthe fluid outlet 25 of the filter holder 2 in the outflow direction A.When the filter element 3 is flowed around, particles 33 are separatedfrom the fluid L to be filtered on the wall 30 of the receiving section19 with the aid of centrifugal force that can be removed from thereceiving section 19 via the particle discharge opening 26. Theparticles 33 can fall out of the particle discharge opening 26, forexample, or be sucked out of same. In comparison to a circular crosssection, the oval-shaped cross-sectional geometry of the receivingsection 19 results in favorable particle separation while at the sametime rendering the system suitable for installation spaces withnon-circular or square cross section.

As FIG. 11 also shows, the maintenance cover 23 has a tubular,particularly oval-tubular incident-flow guard 48 in which the filterelement 3 is received at least partially, preferably such that a flowgap of several millimeters is produced between filter element andincident-flow guard. The incident-flow guard 48 can be embodied in amaterially integral manner with the maintenance cover 23 and, inparticular, prevents particles pre-separated by the rotating flow fromstriking the filter body 4, for example through gravitational effects.

FIG. 12 shows a schematic, perspective view of another embodiment of afilter arrangement 1. The embodiment of the filter arrangement 1according to FIG. 12 differs from the embodiment of the filterarrangement according to FIG. 1 merely in that the fluid inlet 24 doesnot have an oval-shaped but a circular cross section.

FIG. 13 shows a schematic, perspective view of another embodiment of afilter arrangement 1. The embodiment of the filter arrangement 1according to FIG. 13 differs from the embodiment of the filterarrangement 1 according to FIG. 12 in that the fluid inlet 24 ispositioned such that the inflow direction E of the fluid L to befiltered is arranged perpendicular to the direction of the narrowerextension and not perpendicular to the latitudinal direction br thereof.

FIG. 14 shows a schematic, perspective view of another embodiment of afilter element 3. FIG. 15 shows a sectional view of the filter element3, and FIG. 16 shows a front view of the filter element 3. In thefollowing, reference is made simultaneously to FIGS. 14 to 16 .

The construction of the filter element 3 according to FIGS. 14 to 16corresponds substantially to the construction of the filter element 3according to FIG. 6 . The filter element 3 has a first end plate 7 and asecond end plate 8. A folded filter body 4 is positioned between the endplates 7, 8. The end plates 7, 8 are preferably made of cast,particularly foamed polyurethane which encloses the filter body in asealing and form-fitting manner at its axial ends. However, the endplates 7, 8 can also be made of other materials such as injection-moldedthermoplastic plastic and be fused, welded or adhered to the filter body4, for example. The filter body 4 surrounds a lattice-like center tube 5or a winding core. To filter fluid L to be filtered, it flows from anunfiltered side RO of the filter element 3 through the filter medium ofthe filter body 4 to a filtered side RL of the filter element 3. Thefirst end plate 7 has a receiving opening 11 for receiving a secondaryelement 13 through which the filtered fluid also flows according to FIG.7 . The end plates 7, 8 are preferably oval-shaped. The filter body 4can be partially covered by an incident-flow guard 12. The incident-flowguard 12 can be a fine-meshed screen or a film that is welded, adheredor fused to the filter medium. In particular, the incident-flow guard 12adjoins the first end plate 7. The incident-flow guard 12 preventsparticles 33 contained in the fluid L to be filtered entering throughthe fluid inlet 24 from striking the filter medium directly.

The second end plate 8 is preferably fluid-tight, whereby no fluid L canpass from the unfiltered side RO to the filtered side RL of the filterelement 3. The second end plate 8 can have clamping elements 34, forexample, only one of which is provided with a reference symbol in FIG.15 . These can be embodied as elastically deformable extensionsprojecting in the longitudinal direction LR from the end plate 8 that,during the installation of the maintenance cover 23, can be supported onsame and are elastically biased through the installation of themaintenance cover 23. The number of clamping elements 34 is arbitrary.With the aid of the elastically deformable clamping elements 34, thefilter element 3 can be optimally positioned in the receiving section 19of the filter holder 2 with respect to a longitudinal direction LR ofthe filter element 3. The clamping elements 34 also serve to providevibration damping and/or tolerance compensation. The second end plate 8is preferably embodied in a materially integral manner with the clampingelement 34. For example, the second end plate 8 can be made of apolyurethane foam.

A sealing device 10 for sealing the filter element 3 with respect to thereceiving section 19 is provided on the first end plate 7 andparticularly on a front side 9 of the first end plate 7 facing away fromthe filter body 4. The sealing device 10 can be deformed in aspring-biased manner. Preferably, the first end plate 7 and the sealingdevice 10 are embodied in a materially integral manner. For example, thefirst end plate 7 and the sealing device 10 can be made of apolyurethane foam. The sealing device 10 runs completely around thefirst end plate 7. The sealing device 10 is located completely withinthe cross section of the filter body 4, particularly projected in thelongitudinal direction LR.

As shown in FIG. 16 , the sealing device 10 has two first convex curvedsections 35, 36 arranged opposite from one another. The first curvedsections 35, 36 each have a first radius of curvature R35, R36. Theradii of curvature R35 and R36 are preferably of equal size. The radiiof curvature R35 and R36, respectively, have curvature midpoints M35 andM36, respectively. The curvature midpoints M35 and M36 lie on a commonline 37.

The sealing device 10 still has two second convex curved sections 38, 39arranged opposite from one another. The first curved sections 35, 36 andthe second curved sections 38, 39 are interconnected in a materiallyintegral manner. The second curved sections 38, 39 have second radii ofcurvature R38, R39. The second radii of curvature R38, R39 are equal.The curvature midpoints M38 and M39 of the radii of curvature R38 andR39 lie on a common line 40. The line 40 is perpendicular to the line37. The line 37 has a length a₃₇ and the line 40 has a length a₄₀.Preferably, the line 40 bisects the line 37 and vice versa. Preferably,the line 40 and the line 37 intersect at a midpoint through which acenter axis MA of the filter element 3 runs in the longitudinaldirection LR that preferably overlaps with a center axis of the filterholder 2 when the filter element 3 is installed in the filter holder 2.The sealing device 10 still has an outer contour 41. The outer contour41 does not run parallel to an outer contour 42 of the first end plate7. The second radii of curvature R38, R39 are greater than the firstradii of curvature R35, R36. The secondary element 13 can have asimilarly embodied sealing device 18.

It can be seen in FIG. 16 how the contour of the sealing device 10 runsin comparison to a comparative curve VK. In the embodiment specificallyshown, and as also especially preferred, the comparative curve VK runsparallel to the outer and/or inner contour of the filter body 4 and tothe outer and/or inner contour of the open end plate 7 and is morepreferably concentric with respect thereto. In the center of the secondcurved sections 38, 39, the comparative curve has the same distance tothe outer and inner contour of the filter body 4 and to the outer andinner contour of the open end plate 7 as the inner surface 43. As canalso be seen from FIG. 16 , the sealing device 10 has a more pronouncedcurvature in its second curved section 38 than the comparative curve VK.Expressed in another way, in its center, the second curved section 38 ofthe sealing device 10 is at a shorter distance (preferably the shortest)distance to the outer contour of the end plate 7 and of the filter body4 than in the area of the transition from the second curved sections 38,39 to the first curved sections 35, 36. As can also be seen from FIG. 16, the above-described geometry has the effect that the second curvedsections 38, 39 of the sealing device 10 project in an area of overlapinto the curved sections of the end plate 7 and of the filter body 4having a more pronounced curvature.

In this area of overlap UL, the distance of the sealing device 10 orinner surface 43 from the outer contour of the end plate 7 or filterbody 4 is at the maximum. In this way, the width of the end plate 7 canbe exploited in order to achieve maximally pronounced curvature on thesealing device 7 [sic] and thus a good sealing effect.

As shown in FIGS. 17 and 18 , the sealing device 10 has anoval-cylindrical inner surface 43 which forms the sealing surface andabuts in a sealing manner against the engagement area 27 of thereceiving section 19 of the filter holder 2, particularly against acorresponding seal contact surface, when the sealing device 10 engagesin the engagement area 27. Upon engaging in the engagement area 27, thesealing device 10 is deformed in a spring-biased manner, particularlywidened, particularly such that the bias of the sealing device 10against the engagement area 27 is produced exclusively by thespring-biased deformation. The inner surface 43 abuts in a flat andsealing manner against the engagement area 27. With the aid of thecurved sections 35, 36, 38, 39, a constant contact pressure of the innersurface 43 against the engagement area 27 is achieved around theperiphery. Furthermore, as shown in FIG. 17 , the sealing device 10 canhave an approximately rectangular geometry in cross section. Moreover,as shown in FIG. 18 , the sealing device 10 can have two lip seals 44,45 between which a groove-shaped cavity 46 is arranged. As a result, asealing device 10 that is better protected from external influences byhaving a tubular bar on the filter holder side engage in thegroove-shaped cavity such that the inner and/or outer lip seal can beplaced in a sealing manner against the tubular bar. The cavity 46 canpreferably be opened axially for this purpose.

As shown in detail in FIG. 19 and FIG. 32 , the sealing device 10engages in the engagement area 27 of the receiving section 19. The innersurface 43 abuts in a flat and sealing manner against the engagementarea 27, particularly a radially outwardly oriented, oval-cylindricalseal contact surface 270 (see FIG. 32 ). The sealing device 10 thusseals the filter element 3 radially inward with respect to the receivingsection 19. “Inward” is to be understood here as a direction pointingtoward the fluid outlet 25. FIG. 20 shows a schematic, perspective viewof another embodiment of a filter arrangement 1. FIG. 21 shows thefilter arrangement 1 according to FIG. 20 in a schematic partialsectional view. The filter arrangement 1 comprises a filter holder 2 anda filter element 3 arranged in the filter holder 2. A fluid inlet 24 ofthe filter holder 2 is oriented such that an inflow direction E of fluidL to be filtered is oriented in the direction of a longitudinaldirection LR of the filter element 3. The fluid inlet 24 is preferablyarranged on a maintenance cover 23 of the filter holder 2. Any number offluid inlets 24 can be provided.

As shown in FIGS. 21 to 24 , each fluid inlet 24 has a guide member 47for deflecting the fluid L. Each guide member 47 has an angle ofcurvature α. The guide members 47 are set up for the purpose ofdeflecting the inflowing fluid L to be filtered such that, as shown inFIG. 23 with the aid of an arrow 32, it flows around the filter element3 in a helical manner. The filter element 3 is flowed againsttangentially. As a result, particles are separated on a wall 30 of areceiving section 19 of the filter holder 2 that can be discharged fromthe filter holder 2 via a particle discharge opening 26 of the filterholder 2.

The guide members 47 can be embodied as guide vanes. Preferably, anynumber of fluid inlets 24 is provided in a distributed manner around aperiphery u (FIG. 25 ) of the filter holder 2. The angle of curvature αof the guide members 47 can be varied circumferentially around thefilter element 3, particularly in order to generate a uniformlycircumferential flow. The maintenance cover 23 can also have a tubularincident-flow guard 48 as shown in FIG. 24 that is embodied in amaterially integral manner with the maintenance cover 23. Theincident-flow guard 48 prevents the fluid L to be filtered from flowingdirectly against the filter element 3, particularly by separating thefluid inlets 24 from the filter element 3 in such a way that particles33 are prevented from striking the filter medium directly.

FIG. 25 shows a top view of the filter arrangement 1. As shown in FIG.25 , a plurality of fluid inlets 24 can be provided, only two of whichare provided with reference symbols in FIG. 25 . An opening crosssection of the fluid inlets 24 can vary over the circumference u of thefilter holder 2. For example, opening cross sections of the fluid inlets24 can be greater or lesser in regions with pronounced curvature of thefilter element 3 than in regions of the filter element 3 in which it hasa slight curvature.

FIG. 26 shows a schematic, perspective view of another embodiment of afilter arrangement 1. FIG. 27 shows a rear view of the filterarrangement 1. The filter arrangement 1 comprises a filter holder 2. Thefilter holder 2 according to FIG. 26 differs from the filter holder 2according to FIG. 1 through a modified transitional section 49.

As shown in FIG. 27 , a fluid outflow opening 51 of the filter element 3is oval-shaped, and a fluid outlet 25 of the filter holder 2 iscircular. The fluid outlet 25 has a circular cross section facing awayfrom the filter element 3 and an oval-shaped cross section facing towardthe filter element 3. The circular cross section of the fluid outlet 25on the side facing away from the filter element 3 preferably has adiameter that is greater than the small diameter of the oval-shapedcross section on the side of the fluid outlet 25 facing toward thefilter element 3 and/or is greater than the diameter of the sealingdevice 18 in the smaller extension (in the vertical direction hr). AsFIGS. 28 and 29 show in two schematic sectional views of the filterarrangement 1, a transition between the round fluid outlet 25 and theoval-shaped fluid outflow opening 51 of the filter element 3 is achievedthrough a curved transitional section 49 that is arranged between thefluid outlet 25 and the fluid outflow opening 51 of the filter element3. One advantage of the oval-shaped geometry of the fluid outflowopening 51 of the filter element 3 is its large cross-sectional surfacearea. As a result, despite the narrowing between the fluid outlet 25 andthe fluid outflow opening 51 of the filter element 3 shown in FIG. 29 ,there is only a slight disadvantageous effect on the pressure loss.

As shown in FIGS. 30 and 31 , the filter element 3 can still taperconically on the inside; that is, a cross section of a filter medium 4of the filter element 3 enlarges starting from a first end plate 7 inthe direction of a second end plate 8 of the filter element 3. Thisenables an enlarged fluid outlet opening 51 of the filter element 3 tobe achieved in comparison to a filter body 4 that does not taperconically.

REFERENCE SYMBOLS

-   1 filter arrangement-   2 filter holder or filter housing-   3 filter element-   4 filter body-   5 center tube-   6 yarn winding package-   7 end plate, particularly open end plate-   8 end plate, particularly closed end plate-   9 front side-   10 sealing device-   11 receiving opening-   12 incident-flow guard-   13 secondary element-   14 filter medium of the secondary element-   15 end plate of the secondary element, particularly open-   16 end plate of the secondary element, particularly closed-   17 center tube of the secondary element-   18 sealing device of the secondary element-   19 receiving section of the filter holder-   20 housing part-   21 housing part-   22 fastening means-   23 maintenance cover-   24 fluid inlet-   25 fluid outlet-   26 particle discharge opening-   27 engagement area, particularly for the sealing device 10 of the    filter element 3-   28 engagement area, particularly for the sealing device 18 of the    secondary element 13-   29 lateral surface, particularly of the filter body 4-   30 wall, particularly of the receiving section 19-   31 wall, particularly for guiding the flow within the filter holder-   32 arrow, particularly in the direction of circulation around the    filter element 3-   33 particle-   34 clamping element-   35 curved section, particularly with smaller curvature-   36 curved section, particularly with smaller curvature-   37 line-   38 curved section, particularly with larger curvature-   39 curved section, particularly with larger curvature-   40 line, particularly short center line-   41 outer contour, particularly of the sealing device 10-   42 outer contour, particularly of the end plate 7 and/or 8-   43 inner surface, particularly of the sealing device 10,    particularly sealing surface-   44 lip seal, particularly with radially interior sealing edge or    sealing surface-   45 lip seal, particularly with radially exterior or interior sealing    edge or sealing surface-   46 cavity, particularly groove between the lip seals 44, 45-   47 guide member-   48 incident-flow guard, particularly on the maintenance cover 23-   49 transitional section, particularly at the fluid inlet 24-   50 curvature-   51 fluid outflow opening, particularly through the end plate 15 of    the secondary element 13-   270 seal contact surface of the engagement area 27-   280 seal contact surface of the engagement area 28-   a distance-   A outflow direction-   a₃₇ length-   a₄₀ length-   b width-   br latitudinal direction-   E inflow direction-   h height-   hr vertical direction-   L fluid-   LR longitudinal direction-   MA center axis-   M35 curvature midpoint-   M36 curvature midpoint-   M38 curvature midpoint-   M39 curvature midpoint-   RE filtered side-   RO unfiltered side-   R35 radius of curvature-   R36 radius of curvature-   R38 radius of curvature-   R39 radius of curvature-   u circumference-   UL area of overlap-   VK comparative curve-   α angle of curvature

What is claimed is:
 1. A filter arrangement, comprising: a filer elementhaving an oval-shaped cross section, the filter element comprising: anoval-shaped filter medium surrounding a center axis (MA) of the filterelement; a first end plate arranged on a first axial end of theoval-shaped filter medium; a second end plate arranged on a second axialend of the oval-shaped filter medium; wherein the filter medium is afolded filter medium, folded in a zig-zag pattern; wherein a radiallyouter surface of the oval-shaped filter medium (4) forms an oval-shapedradially outer face; wherein the filter element has an incident-flowguard that covers the oval-shaped radially outer face at leastpartially; a filter holder having a receiving section having an ovalshaped wall surrounding the center axis (MA), the oval shaped walldefining and surrounding an oval-shaped interior space of the receivingsection; wherein the filter element is received into the oval-shapedinterior space of the receiving section; wherein the oval-shapedradially outer face of the oval-shaped filter medium has a largestdiameter (b) extending through center axis (MA) to a smallest radiuscurved section of the oval-shaped radially outer face; wherein theoval-shaped radially outer face of the oval-shaped filter medium has asmallest diameter (h) extending through center axis (MA) andperpendicular to the largest diameter (b); wherein a constant radialspacing distance (a) is provided between the oval-shaped radially outerface of the oval-shaped filter medium and the oval shaped wall of thereceiving section around the filter element, forming an oval flow spacehaving a constant radial width (a); a tubular fluid inlet formed on thefilter holder having an inlet flow channel oriented perpendicular to thelargest diameter (b), the tubular fluid inlet positioned to discharge afluid directly into a first end of the oval flow space immediately atthe smallest radius curved section of the oval-shaped radially outerface, such that the fluid is thereby accelerated to flow helically andtangentially around the oval-shaped radially outer face of the filterelement, thereby, separating particles contained in the fluid onto aninterior side of the oval-shaped wall of the receiving section with theaid of centrifugal force; whereby for optimized particle pre-separation,the largest diameter (b) relative to the smallest diameter (h) isbetween 3:1 and 1.5:1; wherein the filter element is covered at leastpartially by an incident-flow guard arranged between the oval-shapedradially outer face of the filter element and the oval flow space,positioned adjacent to where the tubular fluid inlet discharges thefluid into the oval flow space.
 2. The filter arrangement as set forthin claim 1, wherein the incident flow guard is arranged at and liesloosely on the radially outer fold edges of the oval-shaped filtermedium, blocking particles in the fluid from reaching a covered portionof the oval-shaped filter medium.
 3. The filter arrangement as set forthin claim 1, wherein the incident-flow guard is fluid-tight, impermeableto fluid flow through the incident-flow guard.
 4. The filter arrangementas set forth in claim 1, wherein the filter arrangement furthercomprises a secondary element installed into an interior of the filterelement.
 5. The filter arrangement as set forth in claim 1, wherein thefilter element includes a sealing device arranged on the first endplate; and wherein the sealing device is configured to radially seal thefilter element with respect to the filter holder.
 6. The filterarrangement as set forth in claim 1, wherein the incident-flow guardsurrounds the filter element and has an axial length in along the centeraxis of between 15% to 50% of an axial length of the filter element. 7.The filter arrangement as set forth in claim 6, wherein theincident-flow guard is connected to the oval-shaped filter medium or toone of the first end plate or the second end plate.
 8. The filterarrangement as set forth in claim 7, wherein an axial end of theincident-flow guard is embedded into end plate material of the first endplate or the second end plate, securing the incident-flow guard onto thefilter element.
 9. The filter arrangement as set forth in claim 7,wherein the incident-flow guard lies flush on at least a portion of theoval-shaped radially outer face of the oval-shaped filter medium. 10.The filter arrangement as set forth in claim 8, wherein theincident-flow guard is selected from the set consisting of: afluid-tight film, a fluid-permeable fine mesh net, a screen, or a fluidpermeable lattice.